1. Field of the Invention
The present invention generally relates to a ball bearing, and, in particular, to a ball bearing structure for allowing a slider to move smoothly along a straight rail.
2. Description of the Prior Art
A linear motion ball bearing is well known in the art. Such a linear motion ball bearing is typically provided between a straight rail and a slider thereby allowing the slider to move along the rail smoothly, and it is used in various fields, including manufacturing and transporting machinery and robots, whenever relative positional changes between elements along straight paths are required. The linear motion ball bearing is typically comprised of an endless travelling path, which is mostly defined in the slider excepting a load portion which is defined between the slider and the rail on which the slider is mounted for linear motion, and a plurality of balls rollably provided in the endless travelling path, so that the slider can move along the straight rail while the balls roll along the endless travelling path. Thus, with the provision of such a linear motion ball bearing, the slider can move along the straight rail in one direction no matter how long the rail may be, and the slider can also move along the rail back and forth as many times as desired.
Although such a linear motion ball bearing provides excellent in providing a friction-free contact between the slider and the guide rail along which the slider moves, the slider tends to be larger in width than the rail, i.e., in the direction transverse to the direction of movement of the slider, due to the provision of the endless travelling path for the rolling balls. That is, the endless travelling path for the balls includes a load section which is defined as a straight path portion opposite to a guide groove defined in the rail, a returning section extending generally in parallel with the load section and a pair of connecting sections each connected between the corresponding ends of the load and returning sections. The presence of such returning section necessarily tends to make the slider larger in width than the rail so that there are occasions were the application of such linear motion ball bearings is hindered because of this greater width.